In order to elucidate the role of the human I/i blood group system in disease states,the macromolecular species which carry these antigens on the red cell membrane must first be isolated and fully characterized. While it is now well established that I antigenic determinants are carried of glycosphingolipids it is less clear that i determinants are located in similar molecules. Initial attempts to isolate i-active material from human cord erythrocyte membrane will be based on extraction procedures we have used to isolate I-active macrogylcolipid from adult red cell membrane. Alternate isolation procedures will be used if necessary. Isolation steps will be monitored by quantitative immunelectrophoresis (i.e. rocket immuno or affino electrophoresis) and serologically (i.e. hemagglutination inhibition) with anti-i sera, using procedures previously developed in this laboratory. Once the i-active carrier molecule is isolated, the chemical nature of the material will be established using standard biochemchemical procedures. Quantitative assay systems (i.e. quantitative immunoelectorphoretic, radioimmune and radiolabeling assays) will then be developed for the detection of either free i antigen(s) or i antigen(s) on cell surfaces as well as for determining serum levels of anti-i. Attempts to elucidate the relationship between I and i antigens will also be made using crossed immunoelectrophoretic serological and biochemical analysis. Utilizing the information obtained and the reagents and techniques developed from these studies, pilot studies will begin in cooperation with the Department of Haematology and the University Hospital Blood Bank, on the role these antigens (I/i) and /or the antibodies directed against them play in the genesis of disease states (i.e. Sickle cell disease and chronic cold agglutinin disease) or in the appearance of secondary phenomena (i.e. cold agglutinin mediated anemia) associated with a primary disease state (i.e. hemtological or nonhemotological malignancies) which may be useful in the diagnosis of these diseases.